Spinning regenerated cellulose filaments



' Dec. 25, 1956 J. W. PEDLOW SPINNING REGENERATED CELLULOSEI FILAMENTS Filed June 5, 1952 INVENTOR. 2 I JOHN W. PEDLOW r'giz ,6 g

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United States Patent SPINNING REGENERATED CELLULOSE FILAMENTS ApplicationJune 5, 1952, Serial No. 291,933 Claims. 01. 1s 54 This invention relates to methods of spinning artificial filaments from viscose by the wet-spinning system in accordance with which filaments extruded through a spinneret enter an acid coagulating liquid which serves to set up the filaments by removal of solvent and by chemical reaction therewith. More particularly, the invention is concerned with the spinning of filaments from viscose characterized by high tenacity and low dry extensibility such as are' adapted to be used in making tire cords or the like.

-In orderto obtain filaments having high tenacity and low dry extensibility, for instance a dry extensibility in the neighborhood of 10%, it is necessary to subject the filaments to strong stretching while they are in a plastic condition but capable of accepting the stretch without rupture.

It has been proposed to stretch freshly formed filaments from viscose while they are in the acid coagulatingand regenerating bath into which the viscose is extruded. It

has also been proposed to extrude the viscose into a bath at one temperature and conduct the freshly formed filaments directly into another bath at a lower temperature and stretch the filaments in the second bath. These procedures have the disadvantage that is extremely diificult to control the stretch given the filaments in the bath, especially since the stretch is applied while the filaments comprise askin surrounding a fluid core. Non-uniformities in the stretch given the still fragile filaments result in the filaments and enable them to be highly stretched. Use

of the second or so-called stretching bath requires control of two bathsystems as to temperature and, if the non-uniformities,along the length of the final filaments held to a minimum consistent with regeneration of the cellulose to the extent that the filaments have sufiicient strength to withstand stretching without rupturing.

In general, the present improved process involves extruding the viscose, which may or may not be preheated, into a bath comprising an aqueous acid coagulating and regenerating liquid maintained at a temperature between 80 C. and 95 C., withdrawing the filaments from the bath under conditions such that they are not subjected to any appreciable stretching in the bath, conducting the filaments and the hot liquid carried thereby from the bath through the air to a stretching zone, and within one second, preferably Within 0.4 second to 1.0 second, after the filaments leave the bath, stretching the filaments between positively driven rotors and in the presence of thehot coagulating and regenerating liquid carried thereby from the extrusion zone.

The hot coagulating and regenerating liquid carried by the filaments from the bath to the stretching zone serves two important purposes, (1) the heat of the adherent liquid expedites regeneration of the celluloseby the acid and (2) maintains the filaments at an elevated temperature until they are stretched. By stretching the filaments within one second after they are taken from the bath and-in the presence of the hot liquid carried thereby to the'stretching zone 'it is assured that the cellulose is between and 70% regenerated when the filaments are stretched, and that the temperature of the filaments does not drop more than about 12 C. below the temperature of the bath before they are stretched so that the filaments have sufiicient strength and plasticity to accept a stretch up to 100% or higher, without rupture and without treatment thereof with a second bath or plasticizing medium. In the present process, the spinning bath serves, in effect, as both the primary coagulating and regenerating bath and as the secondary stretch bath.

The amount of hot liquid carried from the bath by the filaments is preferably controlled and limited to that amount which will travel with the filaments through the air to the stretching zone at substantially the same speed as the filaments while avoiding irregular disturbances resulting from part of the liquid running back or dripping oif the traveling filament-liquid stream.

A small but substantial quantity of the coagulating and regenerating liquid will adhere as a body to the filaments when they are removed from the spinning bath and under the proper conditions of handling substantially all of the adherent liquid will travel with the filaments second bath comprises a dilute acid solution, the high temperature-low acid bath is highly corrosive and difiic ult to maintain. In addition, the time which elapses between primary coagulation of the viscose and stretching of the filaments is too long to assure optimum results from the stretching.

It is an object of this invention to provide an improved single-bath wet-spinning process for producing regenerated cellulose filaments from viscose which does not require the use of a secondary plasticizing bath for conditioning the filaments for stretching. Another object is to provide an improved process forproducing regenerated cellulose filaments from viscose in which the time which elapses between withdrawal of the filaments from the bath and stretching thereof outside the bath is controlled and at the same velocity as the filaments over considerable distances through the air without any noticeable change of velocity. The amount of liquid that can thus adhere to the filament bundle and be sustained and moved along bodily with it, in spite of gravitational and air friction forces, depends on a number of factors including the particular composition of the viscose, the number of filaments making up the bundle, and the nature of the coagulating and regenerating liquid, particularly its surfacetension, viscosity, and tendency to adhere to the filaments. The maximum amount that can travel with the filaments is not inconsiderable, however, and it has been found that in general relatively small amounts of the hot spinning bath below the maximum possible, will set up the filament forming viscose streams sufiiciently rapidly that the filaments can be stretched within one second after leaving the bath without rupture, and while they are still hot, even when the spinning speed is' higher than is conventional. It is preferred to correlate the conditions so that the hot filaments are stretched while the cellulose comprising them is not more than 70%, preferably not more than 60% regenerated, and the spinning speed iscontrolled so that, under the particular conditions of temperature and viscose and bath' compositions, the cellulose is 50% to 70%, preferably 50% to 60% regenerated in about one second.

According to one embodiment of the invention, in order to limitthe amount of liquid traveling with the filaments the spinneret may be disposed (l) with its orifices discharging upwardly at a predetermined depth of notv over centimeters below the constantly maintained level of the bath, or (2) within a chamber to which the coagulat-' ing and regenerating liquid is supplied and which is, provided with an opening in front of the spinneret face through which the filaments accompanied by the liquid are withdrawn, preferably upwardly or in a generally upward direction. The opening in the chamber may be ofsufiiciently small diameter to limit the amount of liquid passing out of the chamber with the filaments. Depending on the nature of the material forming the opening and the precise contour at the opening, the diameter of the stream issuing may increase or decrease somewhat from the diameter of the opening and therefore the size of the opening should be selected accordingly. The chamber about the spinneret should be kept filled with the coagulating and regenerating liquid which requires feeding the liquid to the chamber at a rate equal to the rate of withdrawal by the filaments. In the vicinity of the opening, the contour of the walls about the passage or zone Within the chamber is preferably streamlined to minimize turbulent flow of the liquid as it approaches the opening immediately before it passes therethrough. This can be achieved by gradually tapering the inside wall or walls toward the opening.

In practicing this embodiment, and to prevent irregularities arising from variations in the effective immersion depth of the spinneret, it is preferred to use a spinneret the holes of which are spaced apart not over about 0.3 mm. (between centers of the adjacent orifices in a given row whether straight or circular or between the center lines of adjacent rows). This precaution is not necessary when good control of the immersion depth is maintained.

To maintain as high as possible a temperature of the filaments at the point of stretching it may be desirable to use a heated viscose in conjunction with the hot coagulating and regenerating bath. The viscose may be preheated to a temperature below that of the bath, preferably to 35 C. to 65 C., immediately prior to being extruded into the hot bath, if desired.

The accompanying drawing is illustrative of apparatus which may be used in carrying out specific embodiments of the spinning process of this invention. In the draw- Figure 1 is a front elevation of one embodiment of suitable apparatus;

Figure 2 is an elevation showing another modification; and

Figure 3 is a view in section of the interior of the housing member of Figure 2.

In Fig. 1, a gear pump 3 is connected, as by a pipe line 4, to a source of supply of viscose which may have the usual cellar temperature of about 20 C. and by pipe line 5 to the swivel joint 6 of a candle filter 7 which is connected by a rounder pipe 8 to a spinneret 9. The pipe 8 may comprise a coiled section 10 which constitutes a heat-interchange section for transferring heat from the hot coagulating liquid in the receptacle 11. The coiled section 10 is below the spinneret so that when the spinneret is swung into the bath the coil is also submerged. When the spinneret is taken out of the bath the coil is removed so that there is no heating of the viscose in the pipe 8 when the spinneret is taken out of the bath as is customary when the pump is stopped for any reason.

The coagulating and regenerating liquid is supplied-to the receptacle 11, whichmay be a trough extending the length of a spinning machine for receiving a plurality of spaced spinnerets along its length, by means of a pipe 12 having one or more outlets 13, each of which may be,

disposed in the vicinity of or below a corresponding spinneret. One or more discharge pipes 14 has or have an overflow opening 15 fixed at a predetermined height to determine the level of the liquid in the receptacle 11. However, the receptacle may be relatively short, and have a length, width and depth to conveniently accommodate a single spinneret assembly entrance connection 13 and overflow pipe 15. Any suitable means, not shown, may be associated with receptacle 11 for maintaining the bath contained therein at the desired temperature between C. and C.

Adjustable detent means 16 may be provided to assure the proper positioning of the spinneret so that the immersion depth A of the orifices is maintained constant and not over 5 centimeters in any event.

Above the receptacle 11 there is supported a withdrawing rotor 17 such as a conventional godet-wheel, which is rotated on the shaft 18. The filament bundle 19 comprising the adherent coagulating and regenerating liquid passes upwardly from the spinneret-through the bath a distance of not more than 5 centimeters and pref erably only 1 to 3 centimeters and then midair a distance of 15 to 75 centimeters, preferably 20 to 35 centimeters, to the rotor 17, carrying a certain amount of liquid with it, the major portion of which is retained by the filaments leaving the rotor and up to the point at which the stretch is applied, (designated (x) in the drawing) beyond which point the excess liquid is stripped off by passing the filaments between the staggered stripping guides 18 and 18a. The filaments are thus stretched between the rotor 17 and reel 19 driven on shaft 20 at a peripheral speed greater than rotor 17. The filaments may be stretched any desired extent but this system is particularly advanta: geous when it is desired to stretch the filaments 75% to or more at elevated temperature. In order to insure that the filaments and at least the major portion of theliquid carried thereby from the spinning bath reach the stretching stage not later than one second after the filament-liquid stream leaves the bath, it is necessary to use a rotor 17 having a radius such that the liquid is not flung off the filaments on the rotor and to limit the number of times the filaments are lapped on the rotor 17 to that number required to provide satisfactory traction and facilitate the stretching.

Liquid stripped from the filaments by the guides 18 and 18a is caught in a receptacle 21. On reel 19 the filaments .may be processed with the usual after-treating liquids such as dilute acid at 60 to 85 C. for completion of regeneration, aqueous sodium sulfide for desulfurizing, water rinses, hypochlorite bleach, antichlors, soft finishes, etc.

In the embodiment shown in Figures 2 and 3, the spinneret is shown disposed within an individual chamber to which the coagulating and regenerating liquid is supplied, although it is to be understood that several spinnerets may be disposed in a common chamber. The spinneret 22 is held in place on a viscose supply pipe 23 by means of the coupling 24, a gasket 25 being present to provide a seal. A housing member 26 is held in place on the coupling member 24 by means of the sleeve 27 which threadedly engages the outer periphery of coupling 24. The member 26 contains the chamber 28 and has a recess 29 within which is fitted a guidingelement 30 having a tapering bore 30a terminating in an orifice 3012. A gasket 31 is seated between the member 30 and the shoulder at the back of the recess 29 and the orificed member 30 is held in place by a coupling sleeve 32 which threadedly engages the outer periphery of the housing member 26. The coagulating and'regenerating liquid is supplied to the housing 26 by means of the conduit 33 which may be the discharge conduit of a metering pump, not shown. The conduit 33 fits into the housing member 26 and is arranged to direct the coagulating liquid around the spinneret 22.-

In using the. apparatus of Figs. 2 and 3, and as shown, it is preferable, when spinning. viscose into acid re'geri crating baths which develop gases during the spinning,- to have a portion or even all of the coagulating liquid stream discharged by the conduit 33 directed across the face 22a of the spinneret in order to prevent accumulation of bubbles at the spinneret face. The arrows generally indicate the flow of the coagulating liquid around the spinneret and theninto the region immediately in front of the spinneret face. The inner end wall of the member 30 projects inwardly of the adjacent inside wall of the housing and this projecting ledge or shoulder assures that the liquid flows from all sides of the outer periphery of the spinneret toward the center of its face. As the liquid flows inwardlyalong the face it contacts with the filaments leaving the several orifices of the spinneret, sweeps gas bubbles from the face and joins with the filaments in the main current of flow axially of the spinneret and of the tapered bore 30a in the guiding member 30. I

The size of the opening 30b may be preselected to limit the diameter of the stream or jet of liquid traveling with the filaments from the spinneret assembly. The guide element or nozzle 30' is preferably made of material which is not only resistant to'co'rrosion, erosion and abrasion and exerts but littleabrading action on any filament that may occasionally rub thereagainst during the initial lacing or threading operations. Glass, porcelain, agate, lava and artificial materials of the latter type such as synthetic sapphire may be used to advantage for this fitting. 'The tapered passage 30a merging into the opening 30b may have any length such as to make the distance from 30b to the spinneret centimeters or less, but is preferably relatively short so that such distance is 1 to 3 centimetsr or less. 1

Control of the coagulating and regenerating liquid to the chamber may. be accomplished either by means of a metering pump suchas a gear pump or by the maintenance of a predetermined pressure on the liquid supplied to the chamber. When dependence is placed upon a predetermined pressuer rather than a metering pump, it then becomes more important to predetermine the diameter of the opening 30b in order to limit the amount of liquid issuing with the filament bundle. Regardless of which system is employed for controlling the supply of coagulating liquid to the chamber it is of paramount importance to keepthe chamber full of coagulating liquid at all times during spinning and also to provide a gradual taper along the bore 30a approaching the opening 30b. This taper assures substantially viscous flow of the coagulating medium through the guide member 30 and into the free flight or course through the air. Some turbulence may be present in thevicinity around the face of the spinneret where the coagulating liquid sweeps transversely of the filaments and .then must change direction to flow through guide member 30, but is preferably minimized by forming the parts, such as member 30 and the spinneret body, with smoothly rounded contours. Whatever ,small amount of turbulence there may be at any part of the passage followed by the coagulating liquid through the chamber, the fact that the liquid is continuously supplied at a. constant rate assures substantially uniform treatment of the filaments within such chamber.

Aspreviously indicated, it is preferred to limit the amount of liquid accompanying the filament bundle traveling through the'airto the stretching zone to the amount which can cohere as a unit and adhere bodily to the given filament bundle throughout its travel Without backflow or dripping so that the liquid at any point along the traveling bundle has substantially the same linear velocity throughout its cross-section as the filaments traveling therein. It is a relatively simple matter to determine when all of the liquid travels at the same speed as the filaments since, when this condition is present, the diamete'r;of the streamremains constant from near the point at which the filament-liquid streams leave the bath to the means which removes theliquid from the filaments beyond the: point at which the stretch is applied. The 'amounflof liquid that can be carried inthis manner optimum results are obtained if the load per filament is i not over 0.0006 gram per centimeter. The latter limit is applicable to bundles having any number of filaments such as 1200. In the spinning of viscose in a dilute aqueous acid coagulating bath having a specific gravity of 1.3 to 1.4, it has been found thatthe limit of load is reached when the filament-liquid stream has a diameter of 3 mm. and optimum results are obtained if the diam eter does not exceed 2 mm.

The amount of liquid in the jet containing the filaments may be controlled in various ways. The size of the opening 30b can be predetermined to limit the diameter of the liquid jet issuing and the velocity of the jet can be controlled by preselectingthe pressure exerted on the liquid in the chamber 28 or by the operation of the metering pump, depending on which means 'of control is employed. When operated in this manner, the size of the opening may vary, for practical purposes, between about 0.5 mm. and 3.0 mm. in diameter, though lesser diameters not exceeding 2 mm. are preferred.

In the embodiments shown, the spinning is performed in a generally upward direction and some reliance may be placed upon the natural tendency of the filament bundle to carry the liquid with it out of the opening, in which event the diameter of the opening can be much larger than and even several times the 3 mm. limit given above if the distance from the face of the spinneret to the liquid level in the exit opening of the chamber is not OVBI'S centimeters and is preferably 2 centimeters or less. The filament-containing jet of liquid issuing acquires its velocity chiefly from the filaments being withdrawn from the assembly. The filament bundle itself can be used to control the diameter of the liquid stream by varying the spacing between the orifices of the spinneret. When thereis used a spacing approaching 0.3 mm. between centers of adjacent orifices in a row and between centers of adjacent rows, a liquid stream of relatively larger diameter will move away with the filaments wherep as a closer spacing such as 0.15 to 0.2 mm. between centers of adjacent orifices in a row and between centers of adjacent rows provides a smaller diameter and, as indicated above, the smaller diameter streams are preferred. 3

As shown in Fig. 2, the spinneret assembly is arranged to discharge the liquid carrying the filament bundle upwardly at an inclination to the vertical and the filamentliquid streams leaving the opening 30b in the housing 26 around the spinneret 22 pass upwardly at an inclination to the vertical to the withdrawing rotor 34, such as a godet-wheel driven on shaft 35. The filaments leaving rotor 34 are stripped of excess liquid by the staggered stripping guides 36 and 36a and then proceed to reel 37, driven byshaft 38 at a peripheral speed greater than rotor 34 and such as to stretch the filaments.

To accomplish the objectives of this invention, it is essential that the filaments retain a substantial amount of the hot liquid carried from the bath until they reach the point at which the stretch is applied, indicated approximately by (x) in the drawing. Loss of liquid by the filaments traveling to the stretching zone may be prevented or held to a minimum by withdrawing the filaments from the bath by means of a rotor having a linear speed substantially the same as that of the filaments and a radius such that no appreciable amount of the liquid is flung off the filaments as the filaments travelaround the surface of the rotor. By selecting the radius of the withdrawing rotor so that the liquid carried by the filaments is held thereon by capillary forces, it is assured. that the filamentstraveling around the rotor are flooded with the coagulating and regenerating liquid and that at least 7 the major portion of the liquid remains with the filament bundle,.is removed with the filaments from the rotor and remains with the filaments until the excess is stripped oif just beyond the point at which the filament-liquid streams leave the withdrawing rotor and stretch is applied to the filaments.

In spinning at shallow immersions :and high spinning speeds in accordance with the preferred embodiments of the invention it is important that the spinning be performed with a minimum of interruptions and therefore it is preferred to spin at a jet stretc ratio (herein defined as the ratio of the linear speed of the yarn at the rotor which draws it from the spinneret to the linear velocity of extrusion) of less than 1 and specifically from 0.2 to 0.9 since it is found that incrustation of the orifices is greatly reduced under such conditions apparently because of the velocity of the viscose itself passing through the orifices. This can be further improved by incorporating in the viscose and/or the hot coagulating and regenerating bath such assistants as the Carbowaxes (e. g. an ethylene oxide polymer of 4000 molecular weight in the bath and/ or such a polymer of 6000 to 9000 molecular weight in the viscose), cation-active compounds such as lauryl pyridinium chloride, the compounds of Collins Patent Nos. 2,359,749-50 andso on.

When a high tenacity product is desired, the viscose, which may be preheated to an elevated temperature below the temperature of the bath and suitably to 35 C. to 65 C. is preferably extruded into an acid regenerating bath at 80 C. to 95 C. containing between 1% and 15% of Zinc sulfate, and the filaments are given a stretch of at least 50% While they are at the elevated temperature resulting from the presence of the adherent spinning bath and in a condition of not over 70% regeneration.

' Regardless of whether filaments of normal strength or of higher than normal strength are produced, the final stretch filaments obtained are characterized by uniform properties.

The following examples in which the percentages given are by weight are illustrative of the invention. The total quality factor referred to is the sum of the products obtained by multiplying the dry (conditioned) tensile strength by the dry (conditioned) extensibility, and the wet tensile strength by the wet extensibility.

' EXAMPLE 1 A viscose having 7.0% cellulose, 5.5% sodium hydroxide and a salt point (NaOl) of 5.0 Was spun at a temperature of 55 C. into aqueous bathcOnt'aining 7.25% sulfuric acid, 12% sodium sulfate and 14% zinc sulfate at a temperatureof 90 C. The spinneret had 60 holes of 0.0025 inch diameter bore and spaced apart 0.006 inch (0.152 mm.) and its face was /2 inch from the start of mid'air travel of the filament stream, which extended over a distance of 33 crns. The spinning was under conditions of 0.86 jet stretch and a draw-off speed of 75 meters per minute at the withdrawing rotor (17 in Fig. l). The withdrawing. rotor had a radius of 3 inches and the filaments were lapped twice th'ereabout, passed between staggeredstripping guides (18, 18a in Fig. l) and passed to a reel (19 in Fig. l) rotated to stretch the filaments The filaments were stretched within 1.0 second after leaving the bath. The major portion of the liquid from the bath remained with the 1650 total denier filament bundle until it was stripped oif and at the point of stretch (x) in Fig. l the bundle had a temperature of 79 C. The final processed and dried yarn had a dry tensile strength of 3.96 gmsJ-denier, and dry extensibility of 10.2%; wet tensile strength of 2.48 gins/denier and wet extensibility of 28.5%. The total quality factor was 111.0.

EXAMPLE 2 Viscose as in Example 1 was extruded at temperatures as shown in the-tablebe'low into baths as in Example 1 but maintained at thetempenaturesgiven in the table. Apparatus as shown in Fig. 1 of the drawing and'described in Example '1 was used. After being stretched 83.5% Within 1.0 second after leaving the bath, and in the presence of the hot spinning liquid carried from the bath, the filaments were processed and dried. They had the properties set forth in the tab-1e.

In all instances, the major portion of the hot coagulating and regeneratingliquid'traveling from the spinning bath with the filament remains with them until the excess is stripped offandat the point of stretch (x) the tilements' have a temperature not lower than about 10 to 12 C. below the temperature of the bath. At the higher temperatures for the viscose, the temperature of the filaments. at (x) is usually less than 10 C. [below the temperature of the bath.

Although the invention has been described in detail in connection with the production of filaments from conventional viscoses, and particularly in connection with filaments having high tenacity and relatively low extensibility such as are useful in the production of tire cords, it is within the scope of the invention to incorporate various modifying materials in the viscose for special purposes. Thus, substances which evolve a gas at elevated temperature, for instance-urea whiohyields carbon dioxide and ammonia in the presence of sodium hydroxide at elevated temperatures and th iourea, which yields carbon disulfide and ammonia under the same conditions, may be mixedwith viscose. Extrusion of the mixture into the coagulating bath maintained at C. to C. and the heating elfect of the hot liquid adhering to the filaments until-they are stretched induces evolution of the gases and results in the" production of sponge-like porous filaments. Also, itis within the scope of the invention to incorporate with the-viscose various materials which react chemically with cellulose to form crosslinks between the cellulose chains such as polyvinyl alcohol, polyacrylamide, and 'dicarboxylic acids. The heat of 'thespinning hath'adhering to the filaments serves to expedite the reaction between the cellulose and the modifier.

The invention has many advantages. The freshly formed filaments in the bath alre'not subjected to a tension other than that required to withdraw thefilaments so that the loadof bath imposed on the filamentsat this stage, when-they are largely constituted of a'thin protective skin of icoagulated cellulose xanthate around a viscose core, is low and the filaments are not subjected to bath dragv resulting .in nonuniform stretching thereof. This makes for a marked increase in the extensibility "of the filaments and permits greater stretching thereof after the withdrawal'from the bath. Also, in thisprooess, the stretch is performed between positively driven rotors rotating at predetermined fixed relative peripheral speeds, which permits precise mechanical-control of the stretch imparted to all portions along the length-of the filaments. This, combined with the use of a spinning bath at 80 C. to 95 C. retention of the hotliquid from-.thcbath by the fibersand stretching of the fibers Within a second after they leawethe bath and in the presence of theliquid so that the temperature of the filaments at the time of stretching'them is not more than "12 C. below thetemperat-ure of the bath, results in fibers of exceptional uni iormity and, when the fibers are highly stretched, in fibers having high tenacity coupled with low extensibility. In addition, a second plasticizing bath is not required even when the filaments are to be stretched up to r100% or higher, thus eliminating entirely the problem of controlling a bath system other than the one into which the viscose is extruded.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. The method of producing artificial filaments which comprises continuously extruding viscose from a spinneret under conditions wherein the jet stretch ratio is from 0.2 to 0.9 into an acid coagulating and regenerating bath having a temperature between 80 C. and 95 C., directing the filament-forming streams in a generally upward direction and Withdrawing the resulting filaments from the bath in said direction, forming the hot coagulating liquid at a point not more than centimeters from the spinneret face into a stream associated with the filaments having substantially the same velocity as the filaments, continuously advancing the filaments and the liquid streams from this point through the air along an upward path a distance of between 15 centimeters and 75 centimeters and then through a helical path, the amount of liquid in the stream being limited to assure that substantially all of the liquid adheres to and travels at substantially the same velocity as the filaments, the laps of the helical path being formed to a diameter of sufiicient size to assure that subsantially all of the hot liquid in the stream remains with the filaments as they proceed through the helical path, stretching the filaments at least 50 percent as they leave the helical path and in the presence of substantially all of the hot liquid initially present in the stream, and then continuously removing liquid from the filaments, the filaments and the liquid stream being advanced from the bath to the point at which the stretch is applied and being stretched in a time interval not longer than about one second.

2. A method in accordance with claim 1 characterized in that the viscose is extruded from a spinneret of which the orifices are spaced apart not more than 0.3 millimeter.

3. A method in accordance with claim 1 characterized in that the liquid stream has a weight per centimeter of from 0.0006 gram to 0.001 gram per filament and a diameter between 0.5 millimeter and 2 millimeters, and the filaments leaving the helical path are stretched 75 percent to 100 percent.

4. A method of producing artificial filaments which comprises continuously extruding viscose from a spinneret under conditions wherein the jet stretch ratio is from 0.2 to 0.9 through orifices or a spinneret spaced apart not more than 0.3 millimeter into a confined tapered passageway having a restricted exit opening not more than 5 centimeters from the spinneret face and a transverse cross-section along a portion thereof decreasing gradually to, and merging with the opening, continuously directing an acid coagulating and regenerating liquid of predetermined composition and having a temperature between 80 C. and 95 C. through the passageway and the opening at a suflicient velocity to form a stream of liquid associated with the filaments issuing from the opening, said liquid stream having a weight per centimeter of length between 0.0006 gram and 0.001, gram per filament and a diameter between 0.5 millimeter and 3 millimeters, continuously withdrawing the filaments and i the stream of hot liquid surrounding the filaments from the opening and advancing them through the air along a generally upward straight path for the distance between 15 centimeters and 75 centimeters and then through a helical path comprising a restricted number of laps which are sufiiciently large in diameter to insure that substantially all of the-hot liquid formed into the stream remains with the filaments as they advance through the helical path, stretching the filaments leaving the helical path from 50 percent to 100 percent in the presence of substantially all of the hot liquid initially present in the stream, and then continuously removing liquid from the filaments, the filaments and liquid stream being advanced from the restricted opening of the confined passageway to the point to which the stretch is applied at a time inerval not longer than one second.

5. A method of producing artificial filaments comprising continuously extruding viscose under conditions wherein the jet stretch ratio is from 0.2 to 0.9 through a spinneret of which the orifices are spaced apart not more than 0.3 millimeter into an acid coagulating and regenerating bath having a temperature between 80 C.

and C., directing the filament-forming streams in a generally upward direction and withdrawing the resulting filaments from the bath in said direction, forming the hot coagulating liquid at a point not more than 5 centimeters from the spinneret case into a stream associated with the filaments having substantially the same velocity as the filaments, continuously advancing the filaments and the liquid stream from this point through the air along an upward path a distance of between 15 centimeters and 75 centimeters and then through a helical path comprising two 360 helices, the amount of liquid forming said stream beinglimited to assure that substantially all the liquid adheres to and travels at substantially the same velocity that the filaments and said helices being formed to a diameter of sufiicient size to assure that substantially all of the liquid remains with the filaments until they leave the helical path, stretching the filaments 75 percent to percent as they leave the helical path and in the presence of substantially all of the hot liquid initially present in the stream, and then continuously removing the liquid from the filaments, the filaments and the liquid stream being advanced from the bath to the point at which the stretch is applied and the filaments being stretched within a time interval not longer than about one second so that the filaments at the time they are stretched have a temperature not lower than about 12 C. below the temperature of the bath into which the viscose is extruded.

References Cited in the file of this patent UNITED STATES PATENTS Re. 22,178 Oppenlaender Sept. 15, 1942 2,076,801 Thurmond Apr. 13, 1937 2,369,190 Thurmond Feb. 13, 1945 2,510,135 Pedlow et al. June 6, 1950 2,536,093 Coleman et a1. Jan. 2, 1951 2,536,094 McDermott et al J an. 2, 1951 2,586,970 McDermott Feb. 26, 1952 2,594,496 Richter Apr. 29, 1952- 2,611,928 Merion et al Sept. 30, 1952 

1. THE METHOD OF PRODUCING ARTIFICIAL FILAMENTS WHICH COMPRISES CONTINUOUSLY EXTRUDING VISCOSE FROM A SPINNERET UNDER CONDITIONS WHEREIN THE JET STRETCH RATIO IS FROM 0.2 TO 0.9 INTO AN ACID COAGULATING AND REGENERATING BATH HAVING A TEMPERATURE BETWEEN 80* C. AND 95* C., DIRECTING THE FILAMENT-FORMING STEAMS IN A GENERALLY UPWARD DIRECTION AND WITH DRAWING THE RESULTING FILAMENTS FROM THE BATH IN SAID DIRECTION, FORMING THE HOT COAGULATING LIQUID AT A POINT NOT MORE THAN 5 CENTIMETERS FROM THE SPINNERET FACE INTO A STREAM ASSOCIATED WITH THE FILAMENTS HAVING SUBSTANTIALLY THE SAME VELOCITY AS THE FILAMENTS, CONTINUOUSLY ADVANCING THE FILAMENTS AND THE LIQUID STREAMS FROM THIS POINT THROUGH THE AIR ALONG AN UPWARD PATH A DISTANCE OF BETWEEN 15 CENTIMETERS AND 75 CENTIMETERS AND THEN THROUGH A HELICAL PATH, THE 